Hitherto aromatic compound such as benzene, toluene, xylene or the like is produced mainly from naphtha. As production methods for naphthalenes, a non-catalyst method such as a solvent extraction process for coal or the like and a gas thermal cracking process for natural gas, acetylene or the like are employed.
However, according to these conventional methods, only several percents of benzene or naphthalenes can be obtained relative to a raw material such as coal, acetylene or the like. Additionally, much by-product aromatic compounds and hydrocarbons, tar and insoluble carbon residues are produced, which offers problems. Additionally, there is such a drawback that the solvent extraction process for coal or the like requires much organic solvent.
As a method of producing aromatic hydrocarbon such as benzene, naphthalene or the like and hydrogen from lower hydrocarbon, particularly methane, a method of reacting methane in presence of a catalyst or in absence of oxygen or an oxidizing agent is known (see, for example, Non-patent Citation 1). As the catalyst in this case, molybdenum carried on ZSM-5 is assumed to be effective. However, in case of using the catalyst, there are such problems to be solved that a catalytic activity is remarkably lowered owing to carbon deposition, and a methane conversion rate is low.
As a measure for solving the above problems, Patent Citation 1 discloses a method for producing aromatic compound and hydrogen from lower hydrocarbon such as methane, ethane or the like, in which CO2 or CO is added to a gas to be reacted thereby suppressing carbon deposition as a side reaction thus stably producing aromatic hydrocarbon such as benzene or the like for a long time, while suppressing a catalytic activity lowering due to a reaction. Patent Citation 2 discloses that hydrogen is added to a raw material gas thereby stably carrying out a catalytic reaction for a long time. Additionally, Patent Citation 3 discloses that a contact reaction for producing aromatic hydrocarbon from lower hydrocarbon and a catalyst regeneration reaction for regenerating a deteriorated catalyst are alternately repeated thereby stably producing aromatic hydrocarbon and hydrogen.